1. Field of the Invention
The present invention relates to apparatus attendant electrofishing and, more particularly, to a barrier for shielding an electrode used in electrofishing.
2. Description of Related Art
Portable electrofishing units have been used for many years. Such units include an electronic power system incorporating a power source and a signal generator for generating the signal or pulse train to be transmitted between a submerged anode electrode and a submerged cathode electrode. Usually, the electronic power system is of a backpack configuration carried by an operator. A trailing wire is suspended from the backpack and includes a bare conductor disposed beneath the water surface and serving as a cathode electrode. The operator wields a wand or pole supporting a bare hoop like element serving as an anode electrode and disposed beneath the water surface. Electrofishing equipment which provides two hand held electrodes is also available as some operators prefer to hold the anode electrode in one hand and the cathode electrode in the other hand. The voltage applied between the anode and cathode electrodes, which voltage may be in the range of 500 to 1000 volts, establishes an electric field within the water. It is well known that fish responding to an electric field are attracted to the anode electrode and repelled from the cathode electrode. Any fish experiencing a voltage gradient along a radial from the anode electrode, which voltage gradient is greater than the rheobase voltage of the fish, will have a neuromuscular reaction. The neuromuscular reactions are stepwise incremental as a function of the stimulation resulting from increasing field strength. These incremental neuromuscular reactions are categorized as follows: a) produces random swimming stimulation above the rheobase voltage (electrotaxis); b) at a higher threshold of stimulation in a dc field, the fish will swim toward the anode electrode (galvanotaxis); c) at a yet higher threshold of stimulation, muscular activity ceases (flaccidity) and the fish becomes unconscious (it does not react to external stimulation, such as being touched or handled); and d) at maximum stimulation, the fish becomes completely rigid (tetany, tonic contractions), even to the point of muscular quivering (clonic contractions).
The greatest voltage gradient across the fish occurs when it is aligned with a radial from the anode electrode and the lowest voltage gradient across the fish will occur when it is broadside to a radial from the anode electrode. Other complex factors, such a different species having different flesh and therefore electrical conductivity, also affect the distance from the anode electrode at which the voltage gradient affecting the fish exceeds the rheobase voltage of the fish. Direct contact by the fish with the anode electrode increase the possibility of injuries of a severe nature or death.
The configuration of the anode electrode affects the distribution of power and the resulting electric field. Is has been determined empirically that an anode electrode shaped as an open ended circular loop or as a diamond shape works admirably well. However, for particular purposes or in particular locations, elongated or specially configured anode electrodes may provide the results sought.
Because of the high voltage between the anode and cathode electrodes, a safety hazard to an operator, usually wading in a pond, lake, stream or other body of water, exist. Should the operator inadvertently contact the bare anode electrode, shock and unconsciousness may occur and result in injury or drowning. Should the bare anode and cathode electrodes contact one another, the resulting short circuit may damage the signal generating equipment and/or power supply and render the electronic power system inoperative. When a second operator is employed to net the fish drawn to the anode electrode, inadvertent contact with the anode electrode may occur directly or through contact with the net frame held by the second operator. The results could be devastating.